Each year millions of cigarette smokers in the U.S. try to quit smoking, but the vast majority relapse within the first few days or weeks of the cessation effort. Sustaining abstinence through the initial weeks of a cessation effort, particularly the first two weeks, is associated with a precipitous decline in relapse risk. Indeed, there is substantial correlational evidence in the literature on smoking and other drug abuse supporting strong associations between the duration of prior abstinence and relapse risk. Our group has conducted a series of laboratory and quasi-laboratory studies designed to rigorously and experimentally examine the relationship between early and later abstinence in cigarette smokers. In our model, a contingency-management (CM) procedure provides experimental control over the amount of early smoking abstinence achieved by smokers who are not trying to quit, but are willing to abstain as part of a study. Collectively, the results of these studies support a direct, causal relationship between early and later abstinence. The next step in developing an experimental literature on this topic in smokers is to move into a treatment-seeking population. In the proposed study, we will use a CM procedure to experimentally manipulate the amount of abstinence achieved during the initial two weeks of a quit attempt by treatment seekers. Participants will be randomized to earn monetary payments contingent on smoking abstinence verified by 1x/day CO monitoring (contingent condition) or independent of smoking abstinence (control condition) during a 14-day abstinence-monitoring period. Nicotine withdrawal, the relative reinforcing effects of smoking, and related measures will also be assessed daily. Follow-up assessments will be conducted 1 and 3 months after treatment entry to assess smoking status. The primary hypothesis is that by increasing early abstinence via CM in the contingent condition, longer-term abstinence will also increase relative to the control condition. In addition, we will examine how dynamic changes in nicotine withdrawal, the relative reinforcing effects of smoking, and related measures during early abstinence may relate to relapse risk. Overall, the proposed study has the potential to effectively contribute new information on the direct relationship between early and later abstinence in smoking-cessation treatment seekers. Such information is essential for the development of an experimental literature in this area and may ultimately lead to more focused and effective interventions to target one of our nation s major public health problems.